Abstract: A roll assembly for use in rolling a wire rod includes an arbor which has a slightly tapered periphery at the middle portion thereof, a liquid pressure applying channel provided in the arbor extending to the tapered periphery, a cemented carbide sleeve securely fitted about the tapered periphery, opposing tightening means securely holding the sleeve by constricting it at around both ends, and a roll neck bearing mounted around each end portion of the arbor.For assembling the roll assembly, liquid pressure is applied through the channel provided in the arbor so as to form a liquid layer between the sleeve and tapered periphery of the arbor.